464Barium (Ba) is a silver-white metal that makes up 0.05% of the Earth’s crust. Very small amounts of naturally occurring barium are sometimes present in food and drinking water. Two barium compounds barium sulfate and barium carbonate are often found in underground deposits. Naturally occurring levels of barium are very low. Groundwater erosion of sedimentary rocks is the primary source of naturally occurring barium in drinking water. Natural soil erosion releases barium into the air. The air most people breathe contains less than 0.0015 parts of barium per billion parts (ppb) of air. Barium and barium compounds are used for many commercial processes. Barium sulfate is mined and used in oil and gas production, medical procedures, and the manufacture of paints, bricks, tiles, glass, and rubber. Other barium compounds are used in the manufacture of ceramics, pesticides, and oil and fuel additives. Barium can enter the body in three ways: through consumption of certain foods and/or drinking water; by inhalation of airborne barium compounds; and through direct skin contact with material containing barium. The latter is a rare occurrence, unless working in a chemical laboratory or similar occupation. Persons working in industries that manufacture or use barium compounds may also be exposed to barium in the air. Such exposure may be hazardous. The amount of barium in food and water supplies poses little or no health concern. In fact, the human body requires a certain level of barium in order to maintain good health. Barium is not a carcinogen, according to the most recent research. The Environmental Protection Agency has established a maximum level of 2 parts of barium per million parts (ppm) of water. Federal agencies like the Occupational Safety and Health Administration regulate barium releases in both water and workplace air in order to protect human health and the environment.